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Post by dustinmattison on Nov 27, 2015 4:19:09 GMT -8
Does anyone have any suggestions on how to build a bell for this? This is an 8 inch J tube on left with the exhaust on right.
I was planning to put a 30 gallon water container in the bell to heat water. (the stainless steel tubing would be placed inside the water container.)
I only have about 70cm between the top of the riser seen below and the roof, so I think I need to make the bell wide.
Or I can wrap the high temp stainless steel corrogated tubing inside the bell to get heat that way. I know it isn't recommended but it will be an open system so I don't see how there could be an explosion or pressure. The right tube goes down into the bench.
I might try to get the gasses to go into the bench in the 3.5 meter round room. The bottom left is a cleanout. The bottom tube goes into the house. The right tube I am going to fill in with sand or try to use both to get extra heat into the mass below the water storage tank. (may be it will help keep the water warm?) The left tube will connect with the bottom.
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Post by dustinmattison on Nov 29, 2015 20:47:53 GMT -8
Dear All,
How do the calculations for ISA change if you have 2 bells? The second bell will be under the floor in my bathroom. I have an 8 inch J tube. Does the size of the ISA of the first bell change if I want to add a second bell under the floor in a very small shower room? If so, how do I calculate the size for these 2 bells?
Dustin
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Post by dustinmattison on Nov 29, 2015 21:04:45 GMT -8
peterberg In the quote below you mention that a bell can be made smaller to compensate for drag. I am still not clear on whether a bell has to be big for it to work. If the bell is smaller than the recommended size, would the heater still work? I am trying to build a water heating system like the Sun Dog safe way to heat water example. If my ISA is not as big as recommended, will the water still heat up? If I understand the calculations correctly, I would need a cylinder that is 2 meters high and 1 meter in diameter for my 8 inch J tube system. That seems too big! I don't know if I can find enough space to make it that big. Is my calculation correct? I used this calculator and assumed I need 8m2 surface area Dustin
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Post by daniel on Dec 18, 2015 8:13:32 GMT -8
Hi Dustin,
Stainless steel has one the lowest heat conductivity values of all the metals, so much lower than it will transfer very little heat to the water inside, I would rather go with copper tubing put around the bell or above the bell, depending on the temperature you want to achieve. For radiant floor heating you don't need a very high temperature. I have seen and installed copper tubing above the heater in a coil and have seen it done on the walls of masonry heaters with bells. The coil was covered in sand. I would go this way for the heat transfer. Hope this helps
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Post by daniel on Dec 18, 2015 8:57:38 GMT -8
Dustin, are these walls reinforced with something, how do they handle seismic activity when needed?
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Post by dustinmattison on Dec 19, 2015 18:01:26 GMT -8
daniel the walls are eartbags with barbed wire and rebar for reinforcement. I followed the eartbag dome house building method
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Post by dustinmattison on Dec 19, 2015 18:20:12 GMT -8
Hi Dustin, Stainless steel has one the lowest heat conductivity values of all the metals, so much lower than it will transfer very little heat to the water inside, I would rather go with copper tubing put around the bell or above the bell, depending on the temperature you want to achieve. For radiant floor heating you don't need a very high temperature. I have seen and installed copper tubing above the heater in a coil and have seen it done on the walls of masonry heaters with bells. The coil was covered in sand. I would go this way for the heat transfer. Hope this helps daniel I bought stainless steel because it has a higher resistance to high heat. I will try and see how it works.
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Post by daniel on Dec 20, 2015 1:40:18 GMT -8
Hi Dustin,
In my experience in building a bell I found out that if you have a smaller bell of course the system will work better but you will have less surface area for heat accumulation. Now from what I have read extensively about bells and benches is that, and there is a possiblility that I am wrong, with the barrel method the top gap is small about 2" which allows for the hot gases to expand and create the draft to travel through the long bench wihout reducing the draft. In bells you have a much higher area above the riser about 12" minimum where the hot gases will rise and remain while allowing the cooler gases to descend and exit. So in my view they work totaly in a different way. In barrell bench design the accumulation is in the length of the bench, in the bell is in the ISA of the bell if you combine them you will have too much surface area and the system will most likely not draw enough for a good combustion (second bell 85% of first bell)
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Post by daniel on Dec 20, 2015 1:44:46 GMT -8
I choose a bell over a bench because of space considerations. However a bell is much more expensive to build than a bench.
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Post by pinhead on Dec 21, 2015 17:00:06 GMT -8
I choose a bell over a bench because of space considerations. However a bell is much more expensive to build than a bench. What makes you say building a bell is more expensive than a bench? How about a bell-bench using half-barrels?
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Post by daniel on Dec 23, 2015 10:48:00 GMT -8
Hi Pinhead,
To me a bell has more meaning when it accumulates in its masonry mass, the rocket does the accumulation in its bench mass but it does not stratify or separates between hot and colder gases. The bench is made using cheap galvanized pipe which you can even make yourself, clay and stones..... If you make bells out of barrels then you would have no mass for heat accumulation. This is what I meant
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Post by pinhead on Dec 23, 2015 11:41:27 GMT -8
Hi Pinhead, To me a bell has more meaning when it accumulates in its masonry mass, the rocket does the accumulation in its bench mass but it does not stratify or separates between hot and colder gases. The bench is made using cheap galvanized pipe which you can even make yourself, clay and stones..... If you make bells out of barrels then you would have no mass for heat accumulation. This is what I meant I'm not sure why you believe the barrel method would have no mass for heat accumulation; this pic was taken before the bell system was finished. Once the bench was finished we had used approximately 2 tons of clay and sand on top of and around the barrels. The mass holds heat well over the night and into the morning. Another pic, before we built the stove and finished the surface:
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Post by daniel on Dec 23, 2015 15:31:34 GMT -8
I was reffering to the metal barrels in a more common type of rocket stove with a metal barrel above the riser and the long bench for mass. The bell I had in mind was a masonry bell with at least 12" of space above the riser which would have been harder to build. My understanding of a bell is a space with heat accumulation mass and enough space for the hot gases to rise and stay and release heat to the surrounding mass while allowing the cooler gases below to exit. If both hot and cold gases travel together it is some type of flue system. As to how high that space has to be to allow the gases to stratify I can't give give you a precise dimension but in my understanding it has to be higher than half barrel. Just to make sure we are talking about the same thing her, in the above pictures you mention a half barrel bell? I don't think that structure could work as a bell from what I see there, it could be a very well heated bench made of half barrels which indeed could be cheap to make but.
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Post by daniel on Dec 23, 2015 15:36:05 GMT -8
I just wanted to add that my bell is about 2.1 meters high and has about 30 cm above the 1.44 meters high heat riser. Being made out of bricks and refractory bricks and refractory concrete it was definitely harder and more expensive to build than if I had chosen a heated bench design.
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Post by pinhead on Dec 24, 2015 8:53:18 GMT -8
In order for a bell to work, you have to have 4x the CSA of the inlet/outlet. This can be demonstrated in this bench design by simply measuring the temperatures across the surface - with a flue design, the bench will get cooler towards the chimney but with a bell design such as this the surface temperature is exceptionally even across the entire length. A simple way to make a taller (and cheap) bell is to build clay-sand-ash "walls" and use the barrels for support on the roof. donkey32.proboards.com/thread/716
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